The present invention relates to a process for the manufacture of synthetic resinous plates, films, sheets, strips, rods, molded parts or shapes of high mechanical strength from thermoplastic synthetic resinous materials. The thermoplastic material is initially heated, in an extruder or a similar installation equipped with a heating and a mixing device, to or above its melting or softening point, the extruded mass leaving the extruder or extruderlike installation, is cooled entirely or partially to a temperature below the melting or softening point, and subsequently in an accessory installation it is exposed to a further processing process. According to the invention, during or after the cooling process, the thermoplastic material is subjected in a forming device, compression molding or another accessory installation, to compression deformation or compression stretching at high pressures (as a function of the synthetic resinous material and the temperature of the extruded mass) and/or to a pulsating pressure or shearing pressure treatment, with the compression formed or shear pressure treated synthetic resinous mass subsequently being subjected to at least one further tempering process, preferably a cooling and/or processing routine. The pressure treatment produces a flow process effecting a stretching. The invention further relates to an apparatus for the execution of the process.
A structure-forming process is already known from DE-OS No. 28 56 580, which is carried out in the forming tool by means of a special pressure deformation during cooling after the original molding or after a subsequent deformation or in a separate working process, whereby in addition to the external configuration desired, simultaneously molecular orientations are produced, which significantly improve the properties of the parts. It is necessary for this purpose to begin with an extruded, cast or injection-molded semi-finished product or preform, i.e., with a preformed synthetic resinous object, which subsequently is stretched under pressure, thereby producing a new, molecularly oriented molded part.